1. Field of the Invention
A cooling system of a V-type multi-cylinder engine, with two cylinder banks arranged in a V formation, typically has a water pump and a confluence pipe arranged on opposite ends of a cylinder head in a lengthwise direction of the engine, i.e., a direction in which a crankshaft extends. The confluence pipe is conventionally provided with a valve casing, having a built-in thermostatic valve. The thermostatic valve and the water pump are in communication with each other, via a passage located between the cylinder banks, so as to supply cooling water, from a radiator, to the water pump via the thermostatic valve, and forward the cooling water, by the water pump, to the water jackets of the cylinder banks. The cooling water discharged from the water jackets is returned to the radiator via the confluence pipe. Such a cooling system is known from, for instance, Japanese Unexamined Patent Publication No 62-91615.
2. Description of Related Art
Because, in the cooling system described in the Japanese publication mentioned above, the water pump and confluence pipe are located on opposite sides of the cylinder head, it is possible to make the piping of the cooling water passages compact. For supplying cooling water to or discharging cooling water from the water jackets, cooling water ports are, in the cooling system disclosed by the Japanese publication mentioned above, provided to admit and expel cooling water to and from the cylinder banks, respectively. Such ports may be provided, for example, in the cylinder heads. For smooth flow of cooling water in the water jackets, so that efficient cooling of a combustion chamber of each cylinder is performed, it is typical to dispose the cooling water ports at the lengthwise opposite ends of each cylinder bank.
However, in the V-type multi-cylinder engine of the Japanese publication referred to above, it is necessary for each cylinder of the cylinder banks to be coupled or connected to the crankshaft. Therefore, the cylinder banks are offset in the lengthwise direction of the crankshaft relative to each other, so as to offset rows of the cylinders of the cylinder banks, and the overall length of the engine becomes greater than the length of each cylinder bank. Accordingly, disposing the cooling water ports so that they project from the ends of the cylinder heads in the lengthwise direction of the engine, and connecting pipes for cooling water passages to the cooling water ports, causes a further increase in overall length of the engine. This makes it difficult to construct the engine so that it is compact.